The American space probe to Mars, Pathfinder, has produced clear evidence that there was once free-flowing water on the planet.

The Pathfinder team, publishing details in the journal, Science, says floods of water appear to have worn down rocks, eroded channels and laid down sediments.

"There is evidence in the pictures for a massive flood event that we saw from orbit from the Viking craft 20 years ago," said Dr John Bell of Cornell University, who has led the team analysing the pictures from Mars.

"You can see ridges and valleys. You can see rocks that are oriented in a certain way; stacked
together as if they've been pushed by a large force and we think that was a
large volume of water.

"You can see hills in the distance that appear to be stratified, maybe indicating that there were multiple flood events that carved
out parts of the landscape," he said.

Tests by the probe's roving vehicle, Sojourner, also show that Martian temperatures can change by 10 degrees Celsius in an hour and just a few centimetres above the surface it is much colder than on the ground itself.

Some of the rocks contain more silica than expected, suggesting that the crust of Mars has been cooked by Earth-like volcanic processes.

"Silicon is a major component of volcanic rocks where the volcanism is explosive as opposed to effusive," said Dr Bell.

"On the Earth, that is thought to reflect plate tectonics and the fact that we have processes on the
Earth that act to enhance the silicon in lava rock.

"So if you were to make the giant leap to planetary significance from a couple of rocks, you might be led
to believe that the crust of Mars is much more processed, much more differentiated, maybe even more Earth-like than we'd thought in the past."

Pathfinder landed in Mars in July, before falling silent 83 days later, probably due to flat batteries.

"The best theory is that the landers battery has died. There is no reason to believe that there is anything wrong with the rover," said Dr Bell.

"After a few days with no contact with the lander, the rover is programmed to start moving around on its
own, on the assumption that the reason the lander is not responding is because it is out of range.

"So it is actually sad when you think about it. It's like a little bear cub searching for its mother. It's wandering around the landing site, waiting for the lander to respond by radio.

"The rover will continue to do that until something breaks in it, because it's solar powered and can start
working every day when the sun comes up," said Dr Bell.

The probe has opened the way for many future probes, some of which will search for life on the red planet and return soil and rock samples to Earth.